1. Technical Field
This disclosure relates to a boost DC/DC converter for supplying electric power on the input side to the output side by synchronizing control of two switching elements.
2. Description of the Related Art
A method for converting electric power at high conversion efficiency using a switching DC/DC converter is widely used in order to convert an input direct-current voltage into a predetermined output direct-current voltage in a power supply device. In the switching DC/DC converter, since a channel is formed by two switching elements placed under synchronous control, the on-resistance of the switching elements is reduced, which enables high efficiency power conversion even under heavy load. In the case of the output voltage being high, the on-resistance of the switching elements can be lowered by setting a voltage controlling the switching elements equal to the output voltage, whereby high efficiency power conversion is achieved.
As for the on-resistance of the switching elements, Japanese Laid-open Patent Application Publications No. H05-83930 and No. 2006-246626 describe reducing the on-resistance of the switching elements by gradually increasing the gate voltage of the second switching element in soft start operation.    Patent Document 1: Japanese Laid-open Patent Application Publication No. H05-83930    Patent Document 2: Japanese Laid-open Patent Application Publication No. 2006-246626
Conventional boost DC/DC converters enable soft start operation by reducing inrush current during the start-up phase. However, there is a demand for higher efficiency power conversion during the start-up phase.